Cyril Marsack initially signed up with the Signals Division in August 1914, but was discharged from camp. He rejoined in 1915 to serve with the New Zealand Rifle Brigade, embarking from Wellington on 5th February 1916. At the time of his enlistment he was working as a Clerk at the Auckland offices of the Northern Steam Ship Company.

After three weeks in Egypt, Cyril Marsack embarked for France. During the next 12 months he spent time with the Battalion in the Field, probably seeing action on the Somme in September 1916. He was also promoted, spent time at the Divisional School and had two periods in hospital, suffering from measles in 1916, and the following year had a bout of mumps.

Cyril Marsack lost his life during the action at Messines on 6th June 1917. His record states that he died in either France or Belgium. He was initially buried at the Rosenberg Chateau Military Cemetery, but in 1930 was re-interred at the Berks Cemetery Extension, Comines-Warneton, Hainaut, Belgium.

In Auckland his death is commemorated at The Auckland Grammar School, at the St Paul’s Church Symonds Street, and on the Roll of Honour at the Auckland War Memorial Museum.